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Search Results: 1 - 10 of 852230 matches for " Prashant Kumar and M S R N Kiran "
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Nanomechanical properties of silicon surfaces nanostructured by excimer laser
Prashant Kumar and M S R N Kiran
Science and Technology of Advanced Materials , 2010,
Abstract: Excimer laser irradiation at ambient temperature has been employed to produce nanostructured silicon surfaces. Nanoindentation was used to investigate the nanomechanical properties of the deformed surfaces as a function of laser parameters, such as the angle of incidence and number of laser pulses at a fixed laser fluence of 5 J cm 2. A single-crystal silicon [311] surface was severely damaged by laser irradiation and became nanocrystalline with an enhanced porosity. The resulting laser-treated surface consisted of nanometer-sized particles. The pore size was controlled by adjusting the angle of incidence and the number of laser pulses, and varied from nanometers to microns. The extent of nanocrystallinity was large for the surfaces irradiated at a small angle of incidence and by a high number of pulses, as confirmed by x-ray diffraction and Raman spectroscopy. The angle of incidence had a stronger effect on the structure and nanomechanical properties than the number of laser pulses.
Graphene produced by radiation-induced reduction of graphene oxide
Prashant Kumar,K. S. Subrahmanyam,C. N. R. Rao
Physics , 2010, DOI: 10.1142/S0219581X11008824
Abstract: Effect of irradiation on graphene oxide by sunlight, UV light and KrF excimer laser has been investigated in detail. Both sunlight and ultraviolet light reduce graphene oxide well after prolonged irradiation, but laser irradiation produces graphene with negligible oxygen functionalities within a short time. Laser irradiation is also useful for one-step synthesis of metal particle decorated graphene. Laser irradiation of graphene oxide appears to be an efficient procedure for large-scale synthesis of graphene.
Nanomechanical Characterization of Indium Nano/Microwires
Kumar Prashant,N Kiran MSR
Nanoscale Research Letters , 2010,
Abstract: Nanomechanical properties of indium nanowires like structures fabricated on quartz substrate by trench template technique, measured using nanoindentation. The hardness and elastic modulus of wires were measured and compared with the values of indium thin film. Displacement burst observed while indenting the nanowire. ‘Wire-only hardness’ obtained using Korsunsky model from composite hardness. Nanowires have exhibited almost same modulus as indium thin film but considerable changes were observed in hardness value.
Synthesis, Characterization, Thermal Properties, and Antimicrobial Activities of 5-(Diethylamino)-2-(5-nitro-1H-benzimidazol-2-yl)phenol and Its Transition Metal Complexes
Vikas S. Padalkar,Vikas S. Patil,Vinod D. Gupta,Kiran R. Phatangare,Prashant G. Umape,N. Sekar
ISRN Organic Chemistry , 2011, DOI: 10.5402/2011/738361
Abstract: Synthesis and antimicrobial activities of new metal [Co(II), Cu(II), Ni(II), and Fe(II)] complexes from 5-(diethylamino)-2-(5-nitro-1H-benzimidazol-2-yl)phenol are described. The newly synthesized ligands were characterized by IR, 1H NMR, and LC-MS analysis, and metal-ligand complex formations were confirmed by using atomic absorption spectroscopy and elemental analysis. All complexes show significant in vitro antibacterial activities against E. coli and S. aureus strains and in vitro antifungal activity against C. albicans and A. niger strains by using serial dilution method. The antibacterial activities were expressed as the minimum inhibitory concentration (MIC) in μg/mL. Thermal properties and electrochemical behavior of novel transition metal complexes have been studied. 1. Introduction Imidazole/Benzimidazole and their derivatives are important class of organic compounds in coordination chemistry, photophysics, photochemistry, bioinorganic chemistry, and bioorganic chemistry [1–7]. 2-(2′-Hydroxyphenyl) benzimidazole (Hpbm) is an important benzimidazole-derived N, O-donor ligand. It’s Zn(II), Be(II), and Al(III) derivatives are photoluminescent [8]. Hydroxyl benzimidazole shows excited-state intramolecular transfer (ESIPT) properties due to acidic protons of phenol and imidazole nitrogen (tautomerism phenomenon). It has been reported that hydroxyl benzimidazole and benzoxazole behave as a structural mimic of DNA base pair for which tautomerism may be initiated at a definite time and position within duplex DNA [9]. Structurally similar natural product bis(benzoxazole) UK-1 has been reported to posses anticancer activity, and the metal-binding studies of UK-1 indicates that benzoxazole-like compound are capable of binding a variety of biologically important metal ions [10]. Benzimidazole derivatives exhibit significant activity against several viruses such as HIV, human cytomegalovirus (HCMV) [11, 12], herpes (HSV-1) [13], and influenza [14]. Benzimidazole derivatives are unique and broad-spectrum class of antirhino/enteroviral agents such as antihistaminic [15], antipyretic [16], antiulcerative [17], antihypertensive, antiviral [18, 19], antitumor [20–24], antihistaminic [25], and antiallergic [26] and are also efficient selective neuropeptide Y Y1 receptor antagonists [27]. Several derivatives are reported in literature for the synthesis of benzimidazole-metal complexes for fluorescent probes and bioorganic application, but antimicrobial activities of these classes of compounds have received little attention. In the literature, there are no reports
Phytochemical Screening and Antimicrobial Activity of the Leaf Extract of Mirabilis jalapa Against Pathogenic Microorganisms
V. Kiran Kumar,N. Ravi Sankar,S. Ramya,R.V. Sahaja
International Journal of Phytomedicine , 2011,
Abstract: Investigation of the phytochemical constituents and antimicrobial activity of the leaf extracts of Mirabilis jalapa were carried out using acetone, chloroform, ethanol and methanol. These extracts were subjected to screening of preliminary phytochemical tests. Phytochemical analysis showed the presence of alkaloids, flavanoids, phenols, glycosides, tannins, saponins and lignins. The methanol extract exhibited the largest zone of inhibition (21mm in dia with 500μg/disc extract) against Staphylococcus aureus and the highest inhibition of fungal radial mycelial growth (97.5% with 500μg/ml medium) against Aspergillus flavus. The methanol extract exhibited the lowest MIC against Staphylococcus aureus (39 μg/ml) and Aspergillus flavus (45μg/ml). It appeared that M. jalapa could be a potential natural source of new antimicrobial agent. Keywords: Mirabilis jalapa, leaf extract, phytochemicals, antimicrobial activity.
Effect of Fly Ash Content on Friction and Dry Sliding Wear Behavior of Glass Fiber Reinforced Polymer Composites - A Taguchi Approach  [PDF]
S.R. Chauhan, Anoop Kumar, I. Singh, Prashant Kumar
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2010, DOI: 10.4236/jmmce.2010.94027
Abstract: The tribological behavior of glass fiber reinforced vinylester composites filled with fly ash particulates were studied using a pin-on-disc wear apparatus under dry sliding conditions. The influence of friction and wear parameters like (pv) factor, sliding distance and percentage of filler content, on the friction and sliding wear rate were investigated. A plan of experiments, based on the Taguchi technique, was performed to acquire data in a controlled way. An orthogonal array and analysis of variance (ANOVA) were applied to investigate the influence of process parameters on the coefficient of friction and sliding wear behaviour of these composites. The Taguchi design of experiment approach eliminates the need for repeated experiments and thus saves time, material and cost. Taguchi approach identifies not only the significant control factors but also their interactions influencing the coefficient of friction and specific wear rate predominantly. The results showed that the inclusion of fly ash as filler materials in glass vinylester composites decreases the coefficient of friction and increases the wear resistance of the glass vinylester composites significantly.
EXPERIMENTAL INVESTIGATION OF PARAMETERS EFFECTING THE NOISE REDUCTION IN HERMITICALLY SEALED RECIPROCATING COMPRESSOR
G.Laxmaiah,Dr. P Ravinder Reddy,M N S V Kiran Kumar
International Journal of Engineering Science and Technology , 2011,
Abstract: Hermetic reciprocating compressors are most commonly used in the refrigeration industry. The main source of noise in refrigerating and air conditioning machinery is the compressor. Reduction of noise in compressors is a complex criterion as many factors such as Shell Thickness, Shell Material, Suction Port Area and Discharge Port Area etc. contribute its effect on the noise and they also interact in a complex manner. In this work a screening test is carried out to find the relative effect of the parameters and their interaction, which can be used as an initial step for further investigations concentrating on the most influencing parameters and their interactions using Taguchi Technique. Here Shell Thickness (ST), Shell Material (SM), Suction Port Area (SPA) and Discharge Port Area (DPA) are chosen as input parameters and the noise is the output parameter. L8 orthogonal array is selected, the factors are assigned and experiments are carried out. Column effect method is used to find the most effective parameters for the noise reduction in the compressor.
CONTROLLED RELEASE FORMULATION DEVELOPMENT AND EVALUATION OF FELODIPINE MATRIX TABLETS BY USING HYDROPHOBIC POLYMERS
S. Kiran Kumar*, T. Ramarao, D.B.R.N. Bikshapathi and K.N. Jayaveera
International Journal of Pharmaceutical Sciences and Research , 2013,
Abstract: Felodipine is a long-acting 1, 4-dihydropyridine calcium channel blocker, used to control hypertension by selective action on peripheral resistance. The conventional felodipine tablet gives a rather high peak and comparatively low trough levels, due to rapid absorption and distribution. More sustained plasma concentrations might thus produce a more even effect on blood pressure. The main aim of the study was to improve dissolution rate of the dosage form in a controlled manner over extended period of 24 hrs. Matrix tablets were prepared by direct compression method,using hydrophobic polymers like Glyceryl monostearate and Carnauba wax. The prepared formulations were evaluated for hardness, thickness, weight variation, friability and in-vitro dissolution studies. Among all the formulations F8 was selected as optimized formulation based on the evaluation parameters and in-vitro release profile of 100% drug release for 24 hrs. The FTIR and DSC results of optimized formulation showed no drug-excipient interaction. For optimized formulation(F8), the drug release mechanism was explored and explained by zero-order (r2=0.984), first-order (r2=0.947), Higuchi (r2=0.967) and Korsmayer-peppas (r2=0.982 & n=0.855) equations, which explained the drug release follows zero-order and is fit for Higuchi equation & mechanism was anomalous diffusion i.e diffusion and erosion.
A study of the synthetic methods and properties of graphenes
C N R Rao, K S Subrahmanyam, H S S Ramakrishna Matte, B Abdulhakeem, A Govindaraj, Barun Das, Prashant Kumar, Anupama Ghosh and Dattatray J Late
Science and Technology of Advanced Materials , 2010,
Abstract: Graphenes with varying number of layers can be synthesized by using different strategies. Thus, single-layer graphene is prepared by micromechanical cleavage, reduction of single-layer graphene oxide, chemical vapor deposition and other methods. Few-layer graphenes are synthesized by conversion of nanodiamond, arc discharge of graphite and other methods. In this article, we briefly overview the various synthetic methods and the surface, magnetic and electrical properties of the produced graphenes. Few-layer graphenes exhibit ferromagnetic features along with antiferromagnetic properties, independent of the method of preparation. Aside from the data on electrical conductivity of graphenes and graphene-polymer composites, we also present the field-effect transistor characteristics of graphenes. Only single-layer reduced graphene oxide exhibits ambipolar properties. The interaction of electron donor and acceptor molecules with few-layer graphene samples is examined in detail.
Optical properties and hardness of highly a-axis oriented AlN films
Feby Jose,R. Ramaseshan,S. Tripura Sundari,S. Dash,M. S. R. N. Kiran,A. K. Tyagi,U. Ramamurty
Physics , 2012,
Abstract: This paper reports optical and nanomechanical properties of seldom studied highly a-axis oriented AlN thin films for the first time. These films were deposited by reactive DC magnetron sputtering technique at an optimal target to substrate distance of 180 mm. Bragg-Brentano geometry X-ray and rocking curve (FWHM = 52 arcsec) studies confirmed the preferred orientation. Spectroscopic ellipsometry revealed that these films exhibit a refractive index of 1.93 at a wavelength of 546 nm. The hardness and elastic modulus of these films were 17 GPa and 190 GPa, respectively. The mechanical properties obtained here are much higher than the earlier reported and therefore can be useful as protective coating in thermo printing devices, piezoelectric films in bulk acoustic wave resonators.
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